Concepts Of Lifetime Fitness

Concepts of Lifetime Fitness

Homeostasis is the state of equilibrium in which the internal environment of the

human body remains relatively constant. Two excellent examples of homeostasis

are how the body maintains a constant temperature and blood pressure during

strenuous physical activity or exercise. Although there are many other

activities in the body that display homeostasis, I will only discuss these two.

Temperature in the human body is usually kept at approximately 37 degrees

Celsius. To maintain such a strict temperature, the body has a few functions to

combat the outside elements. People cannot make themselves cold as readily as

make themselves hot, however I will mention both homeostasis functions. When

the external temperature decreases, a portion of the brain called the

hypothalamus detects the drop by means of the blood. To compensate, the brain

sends chemical and electrical impulses to the muscles. These impulses tell the

muscles to begin to contract and relax at very high intervals. This is commonly

known as shivering. The production of Adenosine Triphosphate or ATP in the

mitochondria of the muscles produces heat. If the body temperature does not

rise immediately after this, then a second function begins. The brain will

signal the blood vessels near the skin to constrict or narrow in diameter. This

occurs so the heat deep in the muscles is conserved. Since the vessels are now

smaller in diameter, less blood is needed to fill them. Since less blood is

needed through the vessels, the heart begins to slow. If the body remains in

this slowed state, hypothermia could result. Hypothermia is the condition in

which metabolic processes are inhibited. The medical world has taken advantage

of this by inducing hypothermia in patients that are undergoing organ

transplants.

To fight temperatures higher than normal, as in exercise or on hot days, the

body reacts in the opposite way than with cold. Again, the hypothalamus detects

the change of temperature in the blood. The brain signals blood vessels not to

constrict, but to dilate. This increases the diameter of the vessels, and

results in the need for more blood. Since more blood is needed to fill the

vessels, the heart pumps faster and that causes respiration to increase. The

increased respiration will make the body exhale some of the internal heat, like

placing a fan in a window to cool a room. The blood vessels are dilated so the

heat deep in the muscles is easily released. Another commonly known mechanism

to fight heat is sweating. Sweat glands found throughout the body are

stimulated by the hypothalamus to excrete sweat and when the sweat evaporates,